The goal of this research is to investigate the "packaging" and the vascular supply to the recurrent laryngeal branch (RLN) of the vagus nerve as factors in the onset of unilateral vocal fold paralysis (UVP). The vocal folds are important for protection of the airway during swallowing and for generating voice. Individuals with UVP, therefore, frequently experience choking while eating and difficulty being heard when speaking. The occurrence of UVP increases with age, occurs more frequently on the left side, and is most often associated with surgical injury, tumor mass, and viral infection that impairs RLN function. In approximately l6-3l percent of all UVP cases, onset of paralysis is idiopathic. The research proposed in this application will address possible connective tissue factors that may explain UVP, particularly in individuals with idiopathic and post-surgical etiologies. Specifically, this research will characterize size and makeup of the "packaging," or epineurium, surrounding RLN nerve fascicles in young and senescent adult human cadavers and make comparisons to previous findings from research using dogs. This research also will characterize the vascular supply to the RLN in humans. Knowledge gained from this research will provide insight into the predisposition of the RLN to ischemia during compression or stretching. Findings from this research may lead to new surgical approaches to protect the RLN from damage during procedures affecting the pharynx, trachea, thyroid gland, esophagus, lungs, and heart. In addition, identification of age-related differences in the protective nerve "packaging" and vascular supply may elucidate tissue factors possibly associated with onset of idiopathic UVP for future anatomic and physiologic investigation using an animal model.